Method of continuously raising and lowering oilfield saft drillstring and twin travelling slips apparatus

ABSTRACT

Disclosed is a method of continuously raising and lowering an oilfield shaft drillstring using a double traveling slips device, wherein two sets of traveling slip mechanism form the two traveling slip mechanisms to form the two traveling slips device, the first set of traveling slip mechanisms and the second set of traveling mechanisms are respectively mounted on a pithead apparatus ( 10 ) to constitute a continuous raising and lowering system. In the process of raising and lowering an oilshaft drill-string, the slips ( 1, 4 ) of each set of traveling slip mechanisms alternately clamp or release the drillstring, ensuring a continuous raising and lowering motion for the drillstring ( 9 ) from beginning to end under the clamping of the slips, and achieving uninterrupted operation. Further disclosed is a double traveling slips device.

CROSS REFERENCE OF RELATED APPLICATION

This is a U.S. National Stage under 35 U.S.C. 371 of the InternationalApplication PCT/CN2013/084585, filed Sep. 29, 2013, which claimspriority under 35 U.S.C. 119(a-d) to CN 201210381451.5, filed Oct. 10,2012.

BACKGROUND OF THE PRESENT INVENTION

1. Field of Invention

The present invention discloses a method for continuously running in andpulling out oil well pipe. The method can be applied to the repairing ofwells, gas wells, injection wells, Pressure drilling operation, or otheroperations. The invention provides a double traveling slips device,which belongs to the technical field of oil field mechanical technology.

2. Description of Related Arts

In the technical field of oil field mechanical technology, theconventional snubbing units have both a stationary slip and a travelingslip which are operated in sequence to grip the pipe as it is snubbedinto the well. The piston rod of the lifting hydraulic cylinder carriesits single traveling slip to realize the reciprocating motion of runningin and pulling out of the pipe. When a column is pulling out of a well,the upward stroke of the piston rod of the cylinder is a working stroke,and its downward stroke is an idle stroke; when a pipe is running into awell, the downward stroke of the piston rod of the cylinder is a workingstroke, and its upward stroke is an idle stroke. The stroke's efficiencyis less than 50%, along with additional power consumption. Thetraditional way of solving this problem is to speed up the idle strokein order to reducing the time of the idle stroke, however, it does notreally solve the problem about time wasted in the idle stroke.

SUMMARY OF THE PRESENT INVENTION

The present invention discloses a method for continuously raising andlowering an oil well pipe. This method solves the problem about thewaste of power and time in an idle stroke, and improves the efficiencyof raising and lowering the oil well pipe.

Further, the present invention provides a double-traveling slip devicefor implementing the above mentioned method for continuously raising andlowering the oil well pipe.

The present invention further discloses a method for continuouslyraising and lowering an oil well pipe. The technical solutions are asfollows:

A technical solution of the method for continuously raising and loweringthe oil pipe comprises following steps of:

-   -   forming a double traveling slips unit by two groups of traveling        slip mechanisms, respectively providing a first group traveling        slip mechanism and a second group traveling mechanism on a        wellhead equipment to form the double traveling slips unit which        is a continuous raising and lowering system;    -   wherein in a process of raising and lowering the oil shaft        drillstring, the slips of each set of traveling slip mechanisms        alternately clamp or release the drillstring, so as to ensure a        continuous raising and lowering motion for the drillstring from        beginning to end under clamping of slips, and achieve        uninterrupted operation.

For both the first set of traveling slip mechanism and the second set oftraveling slip mechanism, stroke of the piston rod of the slip-liftinghydraulic cylinder, the mounting distance between two hydrauliccylinders, the diameters of the cylinders, the diameters of the pistonrods, and the mechanical behaviors are the same or equivalent.

The present invention provides a double traveling slips devicecomprising a first set of traveling slip mechanism and a second set oftraveling slip mechanism. The first set of traveling-slip mechanismcomprises a first slip, a first upper crossbeam, two first slip-liftinghydraulic cylinders and a first lower support beam. The first slip isprovided on the first upper crossbeam. The first upper crossbeam and thepiston rod of the first slip-lifting hydraulic cylinder are fixedtogether and constitute a first gate-shaped frame lifting mechanism. Thetwo first slip-lifting hydraulic cylinders, linked to the first lowersupport beam, are fixed on the pup joint of a wellhead equipment. Thesecond set of traveling-slip mechanism comprises a second slip, a secondupper crossbeam, two second slip-lifting hydraulic cylinders and asecond lower support beam. The second slip is provided on the secondupper crossbeam. The second upper crossbeam and the piston rods of thesecond slip-lifting cylinders are fixed together and constitute a secondgate-shaped frame lifting mechanism. The two second slip-liftinghydraulic cylinders are fixed on the pup joint of a wellhead equipmentvia a second lower support beam. The pipe penetrates the internal holescenter of the first slip and the second slip, and then is inserted intoa wellhead equipment. The gate-shaped frame of the first set oftraveling slip mechanism and the gate-shaped frame of the second set oftraveling slip mechanism are crossing on the top and parallel on twosides, and form a revolving-gate-type structure. Another choice is toput the two first-slip-hydraulic cylinders of the first set oftraveling-slip mechanism on a lateral of the two second-slips-hydrauliccylinders of the second set of traveling slips mechanism. The twofirst-slip-hydraulic cylinders and the second-slip-hydraulic cylindersare connected with a pup joint of a wellhead equipment and in parallelwith two sides of the gates, and form paralleled rectangles with oneoutside the other on one vertical plane.

The above two double-traveling slip mechanisms have the followingcharacteristics: internal holes of both the first slip and the secondslip are closed geometrical shapes such as an internal cylinder, aninternal cone, an internal prism, or a pyramid.

The gate-shaped frame of the first set of traveling slip mechanism andthe gate-shaped frame of the second set of traveling slip mechanism canalso be provided parallel in space to form a cuboid. The first lowersupport beam and the second lower support beam are fixed on pup joint ofa wellhead equipment. The device has characteristics that thecharacteristic of the double traveling slips device: one side of theinternal holes of both the first slip and the second slip are anopen-mouth shape on one end. The width on the open-mouth end is greaterthan the diameter of the pipe.

In the invention, the slips are fixed on the middle of the uppercrossbeam. Two ends of the upper crossbeam are rigidly connected to twopiston rods of the slip-lifting hydraulic cylinders. The slip-liftinghydraulic cylinders are fixed on wellhead equipment or on a supportingbase platform with rigidity by lower support beam, which ensures liftingand pushing powers thereof. The slips, the upper crossbeam, and twohydraulic cylinders of the upper crossbeam constitute a gate-shapedframe mechanism for raising and lowering the pipe. The twoslip-hydraulic cylinders are symmetrically arranged around the centralline of the pipe and stand on the wellhead vertically.

Beneficial effects of the present invention are as follows.

Utilization of the double traveling slips device is capable of solvingthe problem of idle stroke produced by a conventional single-travelingslip device, and eliminating the pausing and waiting time during theidle stroke of the piston rod of the cylinder. If the short time that isspent to clip or release a pipe by turns is neglected, we can considerthat the upward and downward movements of the pipe in the snubbingprocess are continuous, and thus the efficiency is almost doubled. Thedevice increases the efficiency of a workover by two times. Idle strokesof the two slips do not take time alone. When one slip is at the idlestroke, the other one is at the working stroke. By this design, thedevice increases the work time and the efficiency by two times.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a three-dimensional structure schematic view of a doubletraveling slips device having a closed-mouth type of slips andgate-shaped frames crossing in space of the present invention.

FIG. 2 is a first top schematic view of the double traveling slipsdevice having a closed-mouth type of slips and gate-shaped framescrossing in space of the present invention.

FIG. 3 is a first schematic view of the double traveling slips devicehaving a closed-mouth type of slips and gate-shaped frames crossing inspace of the present invention.

FIG. 4 is a second schematic view of the double traveling slips devicehaving a closed-mouth type of slips and gate-shaped frames crossing inspace of the present invention.

FIG. 5 is a second top schematic view of the double traveling slipsdevice having a closed-mouth type of slips and gate-shaped framescrossing in space of the present invention.

FIG. 6 is a third schematic view of the double traveling slips devicehaving a closed-mouth type of slips and gate-shaped frames crossing inspace of the present invention.

Figure: 1—first slip; 2—first upper crossbeam; 3—first slip-liftinghydraulic cylinder; 4—second slip; 5—second upper crossbeam; 6—secondslip-lifting hydraulic cylinder; 7—first lower support beam; 8—secondsupport beam; 9—pipe; 10—wellhead equipment; 11—pupjoint; 12—internalholes on the first slip body; 13—internal holes on the second slipsbody.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Example 1

As shown in FIG. 1, FIG. 3, FIG. 4, and FIG. 6, a double traveling slipsdevice mainly comprises a first set of traveling slip mechanism and asecond set traveling slip mechanism. The first set of traveling slipmechanism comprises a first slip 1, a first upper crossbeam 2, two firstslip-lifting hydraulic cylinders 3, and a first lower support beam 7.The first slip 1 is provided on the first upper crossbeam 2. Two pistonrods of the first slips-lifting hydraulic cylinders 3 are fixed on thefirst upper crossbeam 2 to constitute a gate-shaped frame liftingmechanism. The two first slip-lifting hydraulic cylinders 3, are fixedon a pup joint 11 of a wellhead equipment 10 via the first lower supportbeam 7. The second set of traveling-slip mechanism comprises a secondslips 4, a second upper crossbeam 5, two second slip-lifting hydrauliccylinders 6 and a second lower support beam 8. The second slip 4 isfixed on the second upper crossbeam 5. The two piston rods of the secondslips lifting cylinders 6 are fixed on the second upper crossbeam 5 toconstitute a gate-shaped frame lifting mechanism. The two secondslip-lifting hydraulic cylinders 6 are fixed on the pup joint 11 of awellhead equipment 10 via the second lower support beam 8.

Example 2

As shown in FIG. 1, FIG. 2, and FIG. 3, the first set of traveling-slipmechanism crosses above the second set of traveling-slip mechanism; Inother words, the gate-shaped frame lifting mechanism formed by the twofirst slip-lifting hydraulic cylinder 3 and the gate-shaped framelifting mechanism formed by the two second slip-lifting hydrauliccylinders 6 are crossing in space;

-   -   both the second slips 4 and the first slips 1 provided on an up        end of the second slips are sleeved on the pipe 9 separately;    -   both the second lower support beam 8 and the first lower support        beam 7 provided on an up end of the second lower support beam 8        are fixed separately on a pup joint 11 of the wellhead equipment        10. The pipe 9 penetrates internal hole centers 12, 13 of the        first slips body 1 and the second slip body 4 and then is        inserted into the wellhead equipment 10.

Example 3

As shown in FIG. 4 and FIG. 5: in example 1, the gate-shaped frame ofthe first set of traveling slip mechanism and the gate-shaped frame ofthe second set of traveling slip mechanism are parallel on each side ofthe gates to constitute a cuboid structure. In other words, the twofirst slip-lifting hydraulic cylinders 3 and the two second slip-liftinghydraulic cylinders 6 are parallel. The first slip 1 holds the pipe 9,while the second slip 4 releases the pipe 9 and is back to the idlestroke position. The first lower support beam 7 and the second lowersupport beam 8 are fixed on the pup joint 11 of the wellhead equipment10 separately.

Example 4

As shown in FIG. 4 and FIG. 5, in example 3, the internal hole 12 of thefirst slips 1 body and the second slips 4 body are both open-mouthshapes on one end. A width on an open-mouth end is more than a diameterof the pipe 9, which allows the pipe 9 getting into and out from thefirst slip 1 and the second slip 4 easily.

Example 5

As shown in FIG. 6, in example 1, the gate-shaped frame mechanism of thefirst set of traveling slips and the gate-shaped frame mechanism of thesecond traveling slips are installed in parallel on one vertical plane.In other words, the two first slip-lifting hydraulic cylinders 3 areprovided on a lateral of the two second slip-lifting hydraulic cylinders6; and the two first slip-lifting hydraulic cylinders 3 are parallelwith the two second slip-lifting hydraulic cylinders 6. The first slip 1is provided on an up end of the second slip 4. Both the first slip 1 andthe second slip 4 are respectively sleeved on the pipe 9. The firstlower support beam 7 and the second lower support beam 8 are connectedto the pup joint 11 on the wellhead equipment 10 separately, so as toform the parallel rectangles by sharing the same central axis.

Example 6

In example 2 and example 5, the internal holes 12 of the first slip bodyand the internal holes 13 of the second slip body are closed geometricshapes such as an internal cylinder, an internal cone, an internalprism, or inner pyramid.

In example 1 and example 2, the operating movement status of the devicementioned above is as follows.

(1) Operation of Lifting the Pipe Out of Well:

At the beginning of the operation, the piston rods of the first slip 1and the second slip 4 are both at the lowermost positions of thestrokes. First, the first slip 1 clips the pipe, while the second slip 4is at the release position. Then, the piston rod of the first cylinder 3lifts the first clip 1, which is clipping the pipe, to reach theuppermost position of its stroke. The preparation for pulling the pipeout from a well is thus over.

At the beginning, the first slip 1 and the second slip 4 move on anopposite position: after the second slips clips the pipe, the firstslips releases it immediately. Then, piston rod of the secondslip-lifting hydraulic cylinders 6 lifts the second slips, which isclipping the pipe, to arrive at the middle position of its full strokeand piston rod of the first slip's cylinder 3 carries the first slip 1to decrease to the middle position of the full stroke. Now, the firstslips is at the end of its idling and reaches its working position on acondition that back and forth motions of the piston rods are at the samespeed.

Then the first slip 1 and the second slip 4 perform the divergentmotion: after the first slip 1 clips the pipe, the second slip 4releases the pipe immediately. The piston rod of cylinder 3 of the firstslip, which is clipping the pipe, lifts the first slip 1, to reach itsuppermost position of the full stroke. The piston rod of the secondslip-lifting hydraulic cylinders 6 carries the second slip 4 to reachthe lowermost position of the full stroke. The second slips is at theend of the idle stroke and the beginning of the working position.Carried by the piston rods of the cylinders, the first slips 1 and thesecond slips 4 respectively finish a full stroke separately at the sametime, and then begin to work on a next full stroke.

The pipe is lifted by the lifting operations of convergent motion andthe divergent motion of the first slips 1 and the second slips 4alternately.

When the first slip 1 releases the pipe and is at its downward idlestroke, the second slip 4 clips the pipe and is at its working stroke oflifting the pipe. When the second slip 4 releases the pipe and is at itsdownward idle stroke, the first slip 1 clips the pipe and is at itsworking stroke of lifting the pipe. If ignoring the switching timebetween clipping and releasing, we can consider the lifting of the pipebeing continuous. During operation, the pipe is being clipped all thetime, and the corresponding piston rods of cylinder of the clipped slipare at the upward working stroke. At the same time, the other slipreleases, and its piston rod of the cylinder is at the idle stroke andgetting ready for work. The idle stroke of each slip does not take timealone. It is companied by the working stroke of the other. While oneslip releases, the other clips the pipe. The pipe is being clippedalternately and is in upward movement continuously. The movement of thepipe has no waiting and pausing time, and is continuous.

The pipe is clipped by the first slips 1 and the second slips 4sequentially and is pulled out from a well with the piston rods' motionsof the respective slips' cylinders.

(2) Operation of Lowering the Pipe into Well:

When the pipe is inserted into a well, the first slip 1 and the secondslip 4 are at the lowermost position. Firstly, the second slip 4 clipsthe pipe; the first slip 1 releases the pipe. When the first slip 1 goesup to the uppermost position of cylinder 3 of the slip, the preparationfor operating the pipe down into the well is over.

The convergent motion of the first slip 1 and the second slip 4 beginsat the first. When the first slip 1 clips the pipe, the second slipreleases the pipe rapidly. Then piston rod of cylinder 3 of the firstslip carries the first slip 1, which is clipping the pipe, to decreaseto the middle position of the full stroke, while the piston rod of thesecond slip-lifting hydraulic cylinders 6 carries the second slip 4 torise to the middle position of the full stroke on a condition that theback and forth motions of the piston rod are at the same speed. Then,the first slip 1 and the second slip 4 perform the divergent motion.When the second slip 4 clips the pipe, the first slip 1 releases thepipe immediately. The piston rod of the second slip-lifting hydrauliccylinders 6 carries the second slip 4, which is clipping the pipe, todecrease to the lowermost position of the full stroke. At the same time,the piston rod of cylinder 3 of the first slip carries the first slip 1to rise to the uppermost position of its full stroke, the first slipreturns to an initial position with the idle stroke. In a similar way,they begin to work on the next full stroke.

The pipe is clipped by the first slip 1 and the second slip 4sequentially and is inserted into a well with motions of the piston rodsof cylinders of the respective slips. The movement of the pipe whilerunning into a well is the same as that of the pipe while being pulledout. The utilization on the stroke of piston rods from the two kindstructures of slips lifting hydraulic cylinders are both 50%.

Working conditions of the Example 3 and example 4 are as follows. Asshown in FIG. 4 and FIG. 5, when operating, not only the first set oftraveling slip mechanism and the second set of traveling slip mechanismare running in vertical lifting motion, carried by the slip-liftinghydraulic cylinders, but also are moving in horizontal motions. Thisperformance method allows the slips clip the pipe while moving forwardsand releases it while moving backwards. Because of the characteristic ofmoving away from the working spot, two sets of traveling slip mechanismsdo not interfere and block each other. Because the slip bodies of thefirst slip 1 and the second slip 4 have the open-mouth shapes, the slipscan go forward to clip the pipe and go backwards to release the pipe.The best way of installing the two sets of slip mechanisms is to providethe first slip 1, the first upper crossbeam 2, the second slip 4 and thesecond upper crossbeam 5 on the same level with the two gate-shapedframe mechanisms parallel with each other (see FIG. 4 and FIG. 5). Wecan see: the motions of the first slip 1 and the second slip 4 are thatthe trails of the raising motion and the lowering motion are in paralleland are both parallel to the central axis of the pipe 9 clipped by theslips. The two slips begin to perform a convergent motion from theuppermost and lowermost positions, and then begin to perform adivergence motion after passing through the meeting spot. During themotion, the movement direction of two slips is kept unchanged from startto end, and has no turning point before reaching the uppermost andlowermost positions. Two sets of the traveling slip mechanisms do notinterfere and block each other. The slips go forward to the central axisof the pipe 9 to clip the pipe during its working stroke. The slips backout from the central axis while releasing the pipe during its idlestroke in returning to its initial working position. In one full stroke,the working stroke and the idle stroke of two sets of traveling slipmechanism are alternating with each other and finish pulling out orrunning in of the pipe 9 continuously. With this device, the utilizationon a stroke of the piston rods of the slip-lifting hydraulic cylinder is100%.

What is claimed is:
 1. A method for continuously raising and lowering anoilfield shaft drillstring comprising steps of: forming a doubletraveling slips device by a first set of traveling slip mechanism and asecond set traveling mechanism, respectively providing a first set oftraveling slip mechanism and a second set traveling mechanism on awellhead equipment to form the double traveling slips device which is acontinuous raising and lowering system; wherein in a process of raisingand lowering the oil shaft drillstring, the slips of each set oftraveling slip mechanisms alternately clamp or release the drillstring,so as to ensure a continuous raising and lowering motion for thedrillstring from beginning to end under clamping of slips, and achieveuninterrupted operation.
 2. A double traveling slip device comprising afirst set of traveling ship mechanism and a second set of traveling shipmechanism; wherein the first set of traveling ship mechanism comprises afirst slip, a first upper crossbeam, two first slip-lifting hydrauliccylinders and a first lower support beam, wherein the first slip isprovided on the first upper crossbeam; the first upper crossbeam isconnected with piston rods of the two first slip-lifting hydrauliccylinders to form a first gate-shaped lifting mechanism; the two firstslip-lifting hydraulic cylinders are fixed on a pup joint of a wellheadequipment via the first lower support beam; the other set of travelingslip mechanism comprises a second slip, a second upper crossbeam, twosecond slip-lifting hydraulic cylinders and a second lower support beam;wherein the second slip is provided on the second upper crossbeam; thesecond upper crossbeam is connected with piston rods of the two secondslip-lifting hydraulic cylinders to form a second gate-shaped liftingmechanism, the two second slip-lifting hydraulic cylinders are fixed onthe pup joint of a wellhead equipment via the second lower support beam.3. The double traveling slip device, as recited in claim 2, wherein thefirst set of traveling slip mechanism and the second set traveling slipmechanism constitute a gate-shaped frame crossing in space to form asquare shaped structure, or the two first slip-lifting hydrauliccylinders of the first set of traveling slip mechanism are on an lateralof the second slip-lifting hydraulic cylinder of the second set oftraveling slip mechanism; the first set of traveling slip mechanism andthe second set of traveling slip mechanism are both connected with a pupjoint of a wellhead equipment, so as to form stereo structure withparalleling gate shaped frames having central axis an identical planethe parallel rectangles by sharing the same central axis; the pipepenetrates a center of an internal hole of the first slip and a centerof an internal hole of the second slip and then is inserted into thewellhead equipment.
 4. The double traveling slip device, as recited inclaim 3, wherein internal holes of both the first slip and the secondslip are closed geometry shapes comprising an internal cylinder, aninternal cone, an internal prism and a pyramid.
 5. The double travelingslip device, as recited in claim 2, wherein a first gate-shaped frame ofthe first set of traveling slips mechanism and a second gate-shapedframe of the second set of traveling slips mechanism are parallel oneach side of the gates and form a cuboid.
 6. The double traveling slipdevice, as recited in claim 3, wherein one side of the internal holes ofboth the first slip and the second slip are an open-mouth shape on oneend, and a width of the open-mouth end is greater than a diameter of thedrillstring.